Ovens for many years have used infra-red radiation with usually poor efficiency. Conventional ovens, as is known, utilize a single rod type heating element in the bottom thereof which provides some energy to the lower surface of the food to be cooked but generally cooks by heating the air within the oven. A prolonged preheat time is necessary in order to heat the oven walls which in turn causes convective heating of the air within the oven cavity.
It has been known to provide ovens with separately controlled radiant heating elements disposed above and below the food to be cooked. See, for example, U.S. Pat. No. 4,164,643. In that patent two relatively low wattage and low temperature radiant elements were used and the elements were controlled to operate at optimum wattage settings for various foods. The interior of that oven utilized a shiny aluminum surface to maximize radiation, and the food was preferably baked in a baking container having a blackened outer surface to increase conductivity.
In U.S. Pat. No. 3,249,741 it was recognized that control of the wavelength of the infra-red radiation generated in a baking oven was necessary or desirable. The patent described in general that the longer wavelengths achieved greater penetration before the radiant energy was transformed into sensible heat whereas the shorter wavelengths could exhibit and undesirable crusting on the food product. The patent further describes that the wavelengths and depths of penetration through the products surface layers are inversely related to the temperature of the emitting source and in general described cooking at wavelengths primarily in the ultralong wavelength area of 30-400 microns. The shorter wavelength radiation area was defined as in the range of 0.8 to 30 microns. Sources of radiation were located both above and below the product to be cooked with the end result desired being a complete cooking of the center of the product with only the desired crusting or browning on the outer surface.
In U.S. Pat. No. 4,577,092 a cooking device is described having a removable shroud that can be lowered over the product to be cooked. In this patent the heating element is hingedly attached to the base and resides in the shroud. Therefore, the heating element can be lifted by rotating it backwardly about the hinged attachment of one side thereof to insert or remove food products. This patent describes only a single radiant element located above the product to be cooked.
In U.S. Pat. No. 4,238,669, there is described an oven suited for cooking crusted products wherein two sources of heat energy are provided. A low heat is provided from resistance heaters and a separately controlled source of high heat from quartz lamps is also provided. The high heat is estimated at preferably 1,000.degree. F. per lamp bulb with the low heat coils generating heat at about 500.degree. F.